This invention relates generally to aluminum alloys and more particularly to aluminum alloy conductors.
Heretofore copper wires have been used as the electromagnetic conductors in transformers, motors, etc., conductors for communication cables and conductors for indoor wire exclusively. In more recent times, however, the rise and fluctuation of the price of copper throughout the world has accelerated the desire for the substitution of copper with aluminum as a material for conductors. This substitution is made even more desirous with the increase in need to make electric machines and appliances, cables, etc. lighter. These conditions have quickly called forth brisk activities in an endeavor to use aluminum and aluminum alloy wires for such conductors. Under the circumstances, aluminum alloy wires used for these purposes have come to be required to possess properties similar to those of copper wires heretofore in use. The properties required of such conductors are as follows:
1. As conductors, they are required to have a high electric conductivity, which must not be lower than 60% IACS. PA1 2. as for mechanical properties, they must possess qualities of flexibility suitable for electric wires, ductility and flexibility sufficient to withstand the bending at the time of manufacture and use, and some degree of strength which will withstand the required tension applied thereto at the time of use and manufacture. PA1 3. The manufacturing processes of conductors for coils, conductors for communication cables, conductors for indoor wires, etc. must not be interrupted by batch annealing or the like because the manufacture of electric wires using such conductors is usually carried out in a high speed tandem line of drawing, continuous annealing and insulation sheathing. It is therefore necessary that the heat treatment for obtaining satisfactory properties be done by a continuous process, dispensing with such complicated treatments as quenching, aging, etc.
Heretofore, aluminum for electric purposes, AI-Mg alloys (for example, Alloy 5005) which are called alloys of the work hardening type, Al-Mg-Si alloys (for example, "Aldrey" Aluminum Alloy, Alloy 6201) which are called alloys of the age-hardening type, etc., have been used for transmission lines and distribution lines in the form of an aluminum conductor steel reinforced (known as ACSR), an all aluminum conductor (AAC), an all aluminum alloy conductor (AAAC), an aluminum conductor aluminum alloy reinforced (ACAR), etc. All of these are put to use after cold working, or after such heat treatments as quenching and aging treatment. In spite of their high mechanical strength, they have a very low electric conductivity (52 - 55% IACS), with the exception of electric conductor grade aluminum (electric conductivity 52 - 55% IACS).
The present inventors gave suitable annealing treatments to such alloys with a view toward obtaining a material which has a proper degree of strength. However, the materials thus obtained were not good for the intended purpose because their electric conductivity was as low as 57 - 59% IACS, although they were satisfactory with respect to strength and ductility.
On the other hand, the soft material of electric conductor grade aluminum was found unsatisfactory with respect to strength, its strength being as markedly low as approximately 8 - 9 Kg/cm.sup.2. Furthermore, even when the cold working treatment of 10-odd percent after annealing, which is a technique generally employed in the manufacture of one quarter hard materials, was given, the tensile strength was improved only to about 11 Kg/mm.sup.2 and was found insufficient for use in many instances. If the degree of cold working is increased further, ductility reduces considerably.
There is on the other hand, an aluminum alloy for electric conductors, that is a soft material which is an Al-Fe-Mg-Si alloy developed for use as rotors in rotary machines and is commonly called Cond aluminum alloy. It is recommended as having excellent resistance to creep. (See for example, U.S. Pat. No. 2,572,562) This alloy is of the age-hardening type, the precipitation-phase of Mg.sub.2 Si being a strengthening factor, and contains 0.2 - 1.1 percent Fe, 0.2 - 0.5 percent Mg and 0.05 - 0.15 percent Si. A conductor which is comparatively excellent in strength, electric conductivity and ductility is obtained by adding comparatively large quantities of Mg, Fe and Si, applying heat treatment for a long time at a high temperature of 400.degree.C - 450.degree.C, and then cold working the alloy to an extent of about 10%. However, the necessity of giving heat treatment for a long time at a high temperature becomes a fatal drawback when manufacturing the afore-mentioned magnet wires and conductors for communication cables and indoor wires. That is to say, materials such as this which are not usable in tandem line production make the production cost very high.